1. Field of the Invention
The present invention relates to a torsional vibration damper assembled in a clutch for a manual transmission of a vehicle or a lock-up clutch for an automatic transmission thereof comprising a torque converter.
2. Description of the Prior Art
A torsional vibration emanating from a vehicle engine causes undesired vibration, noise, etc. in a torque transmitting system during operation of the vehicle. For the purpose of eliminating the influence of the vibration, it is well known to provide a clutch or a lock-up clutch with a torsional vibration damper using compression springs acting arcuately of a clutch. However, a problem of presently known vibration damper assembly is that the assembly will only allow a relatively small deflection amplitude.
In order to solve the problem, a torsional vibration damper has been provided in that a pair of equalizers including an annular portion is disposed opposing each other at the both end sides of a hub with a plurality of hub arms extending outward. Arm portions extending outward from the annular portion of the equalizers are positioned between neighboring hub arms of the hub, compression spring sets interposed between the arm portions and the hub arms to form groups of spring sets acting in parallel with each group having spring sets acting in series between neighboring hub arms, whereby a drive plate engaging the compression spring sets has a larger relative turning angle.
According to the above torsional vibration damper, a root of the arm portion is inferior in strength since the arm portion of such known equalizer is shaped like a segment expanding outward from the external periphery of the annular portion.
However, if the arcuate width of the root should be expanded in order to strengthen the root, it would make an angular space for accommodating the compression spring sets narrower, to limit the capability of extending travel of the compression spring sets. Consequently, it is impossible to give a relatively high amplitude damping to the damper.